KR20090131254A - High strength baking hardening type cold rolled steel sheet having excellent aging property and processibility, galvanized steel sheet and the method for manufacfuring thereof - Google Patents

Abstract

PURPOSE: A high strength bake-hardenable cold rolled steel sheet, a galvanized steel sheet, and a method for manufacturing the same are provided to secure superior tensile strength of a high strength bake-hardenable cold rolled steel sheet by limiting P and Al within a proper range and restricting the production of oxide. CONSTITUTION: A high strength bake-hardenable cold rolled steel sheet comprises C 0.0016~0.0030wt%, Si 0.02 wt%, Mn 0.2~1.2 wt%, P 0.01~0.05 wt%, S 0.01wt% or less, soluble Al 0.15~0.3 wt%, N 0.003~0.011 wt%, Mo 0.01~0.1 wt%, B 0.0005~0.0015 wt%, Ti 0.003 weight% or less, and the rest Fe and inevitable impurities. The steel sheet has a baking hardness of 30MPa, an aging index of 30MPa or less, a grain size of ASTM No.9, and a tensile strength of 340~390MPa.

Description

HIGH STRENGTH BAKING HARDENING TYPE COLD ROLLED STEEL SHEET HAVING EXCELLENT AGING PROPERTY AND PROCESSIBILITY, GALVANIZED STEEL SHEET AND THE METHOD FOR MANUFACFURING THE

The present invention relates to a high-strength cold rolled steel sheet, hot-dip galvanized steel sheet and a method for manufacturing the same, which are used in automobile exterior materials, etc. More specifically, the hardening hardening value is 30MPa or more and the Aging Index (AI, Aging Index) value is 30MPa The present invention relates to a cold rolled steel sheet and a hot-dip galvanized steel sheet having improved surface mold suppression methods and formability in the production of plated steel sheets.

In general, as a method for producing a cold-rolled steel sheet having a bake hardenability, low carbon P-added aluminum-killed steel (Al-killed steel) is simply wound at a low temperature, that is, bake hardening by an annealing method using a low temperature winding in a temperature range of 400-500 ° C. The method of manufacturing steel of about 40-50 MPa amount was mainly used. This is because both of the moldability and the baking hardenability are more easily achieved by the annealing. P-added Al-Killed steel by the continuous annealing method uses a relatively fast cooling rate, making it easy to secure the hardening of the hardening, while the formability is deteriorated by rapid heating and short-term annealing. Its use is limited only. Thanks to the recent rapid development of steelmaking technology, it is possible to control the appropriate amount of solid solution in the steel and to manufacture the hardened hardened cold rolled steel sheet with excellent formability by using Al-Killed steel sheet containing strong carbonitride-forming elements such as Ti or Nb. It is increasingly used for automotive exterior materials that require dent resistance.

Japanese Patent Laid-Open Publication No. 1986-026757 discloses Ti and Ti, Nb-compound-added ultra low carbon cold rolled steel sheets having a C 0.0005-0.015% and an S + N content ≤ 0.005%, and in Japanese Patent Laid-Open No. 1982-089437 Disclosed is a method for producing steel having a bake hardening amount of about 40 MPa or more using Ti-added steel of 0.010% or less. This method is to control the amount of Ti and Nb added or the cooling rate at the time of annealing so that the amount of solid solution in the steel is appropriately applied to prevent hardening of the material while providing hardening hardening. However, in the case of Ti, Ti, and Nb composite additive steel, strict control of Ti, nitrogen, and sulfur is required in the steelmaking process in order to secure an appropriate hardening hardening amount, thereby causing a problem of cost increase. In addition, in the case of the Nb-added steel in the patent, workability deterioration due to high temperature annealing and manufacturing cost increase due to the addition of special elements are expected.

On the other hand, as a technique for securing patentability through the addition of new alloying elements, Japanese Patent Laid-Open Publication No. 1993-093502 discloses a method of increasing the baking hardness by adding Sn, and Japanese Patent Laid-Open Publication No. 1997-249936 discloses V By adding Nb with Nb, the ductility improvement effect through stress concentration relaxation of grain boundary is introduced. In addition, Japanese Patent Laid-Open Publication No. 1996-049038 promotes moldability by Zr, and Japanese Patent Laid-Open Publication No. 1995-278654 promotes moldability by minimizing the increase of high strength and deterioration of work hardening index (N) by Cr addition. However, there is a burden of cost increase.

The present invention is intended to reduce the weight of the vehicle body through the high strength of the material for the exterior of the automobile, and by appropriately controlling the alloy component and the manufacturing process, it is a small hardening type cold rolled steel sheet excellent in baking hardenability and room temperature resistance, excellent workability and formability To provide a hot-dip galvanized steel sheet and a method for producing them.

In the present invention, by weight% C: 0.0016 ~ 0.0030%, Si: 0.02% or less, Mn: 0.2 ~ 1.2%, P: 0.01 ~ 0.05%, S: 0.01% or less, Soluble Al: 0.15 ~ 0.3%, N: 0.0025% or less, Nb: 0.003-0.011%, Mo: 0.01-0.1% and B: 0.0005-0.0015%, the remainder is composed of Fe and unavoidable impurities, the content of P and Sol-Al is P≤ -0.06 * ln (Al) -0.0018 / Al-0.055 to satisfy the high strength provides a hard hardened cold-rolled steel sheet.

It provides a hot-dip galvanized steel sheet comprising a hot-dip galvanized layer on the cold-rolled steel sheet that satisfies the composition.

The present invention provides a cold rolled steel sheet and a hot-dip galvanized steel sheet, wherein the bake hardening amount (BH) is 30 MPa or more, the aging index (AI) is 30 MPa or less, and the grain size is ASTM No. 9 or more.

In addition, the present invention is a weight% C: 0.0016 ~ 0.0030%, Si: 0.02% or less, Mn: 0.2 ~ 1.2%, P: 0.01 ~ 0.05%, S: 0.01% or less, Soluble Al: 0.15 ~ 0.3 %, N: 0.0025% or less, Nb: 0.003-0.011%, Mo: 0.01-0.1% and B: 0.0005-0.0015%, the remainder is composed of Fe and unavoidable impurities, the content of P and Sol-Al Heating the steel slab satisfying P ≦ -0.06 * ln (Al) -0.0018 / Al-0.055 at 200 ° C. or higher and then hot finishing rolling at a temperature range of 880 ° C. to 920 ° C .;

Air cooling after winding in a temperature range of 600 to 650 ° C .;

Cold rolling at a reduction ratio of 70-80%;

Continuous annealing at a temperature range of 750 ~ 830 ℃; And

Provided is a method for producing a high strength hardened hardened cold rolled steel sheet comprising a step of temper rolling at a rolling reduction of 1.2 ~ 1.5%.

It provides a method for producing a high strength bake hardened hot-dip galvanized steel sheet comprising the step of hot-dip galvanizing the cold-rolled steel sheet prepared by the above method.

The present invention restricts the oxide generating elements P and Al to the appropriate ranges, and suppresses the generation of oxides occurring along the grain interface or along the grain boundary through the control of the manufacturing process, thereby resulting in a hardening hardening amount (BH) of 30 MPa. As above, the aging index (AI) is 30MPa or less, which is excellent in aging resistance at room temperature, and at the same time provides a high strength bake hardened cold rolled steel sheet and a hot dip galvanized steel sheet having a tensile strength of 340 to 390 MPa.

Hereinafter will be described in detail with respect to the composition range of the present invention (hereinafter by weight).

The content of carbon (C) is 0.0016 to 0.0030%. C is an element showing solid solution hardening and hardening hardening. If the C content is less than 0.0016%, the tensile strength is insufficient due to the very low carbon content, and even if the grain refining effect is achieved by the addition of Nb, the absolute carbon content in the steel is low, and sufficient bake hardenability is not obtained. On the other hand, when the C content exceeds 0.003%, the grain refining effect in the Nb-added steel is greatly increased, so the hardening hardening property is very high, and the room temperature aging resistance is not secured due to the excessive amount of solid carbon, so that the strainer strain occurs during press molding. Moldability and ductility are reduced. Therefore, the content of C is 0.0016 to 0.003%.

The content of silicon (Si) is to be 0.02% or less. Si is an element to increase the strength, the strength increases as the amount added, but ductile deterioration is remarkable, it is advantageous to add as low as possible. In particular, since Si is an element that degrades the hot-plating property, in the present invention, the amount of addition is limited to 0.02% or less in order to prevent material deterioration and plating characteristic deterioration by Si.

The content of manganese (Mn) is 0.2 to 1.2%. Mn is an element that refines particles without damaging ductility, precipitates sulfur in steel completely with MnS, prevents hot brittleness due to FeS formation, and strengthens steel. If the Mn content is less than 0.2%, proper tensile strength cannot be secured. If the content of Mn is more than 1.2%, the strength increases due to solid solution strengthening and moldability deteriorates. In the process, a large amount of oxides such as MnO are formed on the surface, thereby deteriorating the plating adhesion, and a large amount of plating defects such as streaks are generated, resulting in deterioration of product quality.

The content of phosphorus (P) is 0.01 to 0.05%. P is a substitution type alloy element with the largest solid solution strengthening effect, and serves to improve in-plane anisotropy and strength. In addition, P plays a role in facilitating the development of (111) aggregate structure, which is advantageous for improving the average r value in the future annealing step by miniaturizing the hot-rolled sheet grains. Effect), the hardening hardenability tends to increase as the P content increases. However, the P content is limited to 0.05% because the secondary work brittleness may occur due to grain boundary embrittlement due to high P content as well as processability deterioration due to YP increase and EL decrease when the P content is continuously increased. It was.

Sulfur (S) content is less than 0.01%. S is an element which should be precipitated as sulfide of MnS at high temperature to prevent hot brittleness by FeS. If the content of S is excessive, there is a possibility that S remaining after precipitation with MnS embrittles grain boundaries and causes hot brittleness. In addition, even if the amount of S added to completely precipitate the MnS precipitate, when the content of S is large, material degradation due to excessive precipitation occurs, so the amount of addition is limited to 0.01% or less.

The content of soluble aluminum (Sol-Al) is 0.15 to 0.3%. Al is usually added for deoxidation of steel, but in the present invention, it exhibits an effect of doubling grain refining effect and Al hardenability by AlN precipitation. That is, in the present invention, the grain refining effect mainly uses NbC precipitates due to Nb addition, but serves to improve BH properties without deterioration of aging resistance by further minimizing grains by AlN precipitates. In addition, when Al is added in excess of 0.15%, there is an effect of improving the formability by miniaturizing the hot-rolled sheet grains. However, when the content exceeds 0.3%, the Al content is limited to 0.15 to 0.3% because the strength increase and elongation due to the formation of a large amount of Al precipitates decrease and the moldability is deteriorated.

The content of nitrogen (N) is to be 0.0025% or less. N deteriorates the formability of the steel by being in solid solution before or after annealing, and it is necessary to fix with Ti or Al because the aging deterioration is much larger than other invasive elements. As in the present invention, when Nb is properly added along with a small amount of Ti, excessive addition of nitrogen results in generation of solid nitrogen in steel. In general, nitrogen has a very fast diffusion rate compared to carbon, and therefore, when present as solid nitrogen, the deterioration of room temperature aging resistance is very serious compared to that of solid carbon. In addition, since the yield strength increases and elongation and r value deteriorate due to the remaining of solid solution nitrogen, the N content is limited to 0.0025% or less.

The content of niobium (Nb) is 0.003 to 0.011%. Nb is one of the important elements of the present invention. In general, Nb is a strong carbonitride-forming element, which fixes carbon present in the river with NbC precipitates. Particularly, NbC precipitates formed are very fine compared to other steel precipitates, which acts as a strong barrier to grain growth during recrystallization annealing. Will be That is, in the present invention, the effect of miniaturization by Nb is a technique for achieving the hardening hardening by solid solution carbon by using the effect of such NbC precipitates and remaining solid solution carbon in the steel. To this end, it is necessary to properly control the amount of NbC precipitates in the steel and to retain the dissolved carbon in a range that minimizes material degradation. Therefore, in the present invention, the content of Nb proposed to promote grain refining effect by NbC precipitates and to secure quench hardening through proper solid solution carbon residue is limited to 0.003 to 0.011% in consideration of the content of C.

The content of molybdenum (Mo) is 0.01 ~ 0.1%. Mo is a very important element in the present invention. Mo is dissolved in steel to improve strength or to form Mo-based carbides. Above all, however, the important role of Mo is to increase the binding strength of grain boundaries in the presence of solid solution, thereby improving grain boundary breakdown by P, that is, secondary processing brittleness, and suppressing the diffusion of carbon by affinity with solid carbon. To improve. If Mo is less than 0.01%, the above effect cannot be obtained, and if it is more than 0.1%, the effect of improving secondary work brittleness or age resistance is insignificant compared to addition of Mo. Therefore, in the present invention, the content of Mo is limited to 0.01 to 0.1%.

The content of boron (B) is 0.0005 to 0.0015%. When B is an invasive element present in steel, it is dissolved at grain boundaries or combines with nitrogen to form nitride of BN. B is an element having a great influence of the material compared to the added amount, and it is necessary to strictly limit the added amount. That is, when a small amount of B is added to steel, it segregates at grain boundaries and improves secondary brittleness. However, if a certain amount or more is added, it is necessary to add an appropriate range because material deterioration occurs that causes an increase in strength and a significant decrease in ductility. In the present invention, the content of B is limited to 0.0005 to 0.0015% in consideration of such characteristics and steelmaking ability.

In the present invention, titanium (Ti) may be added at 0.003% or less.

Ti is a carbonitride forming element and forms nitrides such as TiN, sulfides such as TiS or Ti ₄ C ₂ S ₂ and carbides such as TiC in the steel. However, in the present invention, Ti is added only at a level of fixing a small amount of nitrogen as 0.003% or less. The reason for presenting a trace amount of Ti content in the present invention is that a very small amount of Ti is contained among various components added to satisfy the material characteristics of the steelmaking industry during actual production. This is because when present, Ti present in the previous tapping material may be contained in the tapping material of the present invention steel. However, in the case of controlling Nb as the main element for improving the aging resistance as in the present invention steel, the addition of Ti is not required, and the BH property decreases when Ti is added, but it is limited to less than 0.003%, which is a very small level in consideration of actual production conditions.

The rest consists of Fe and other unavoidable impurities.

The present invention satisfies the following relationship for controlling the content of P and soluble Al.

P≤-0.06 * ln (Al) -0.0018 / Al-0.055

As mentioned above, P promotes selective oxidation along the grain boundaries of the steel plate surface at high temperatures such as hot rolling. If such selective oxidation is intensified, the risk of causing a defect on the surface of the steel sheet due to the surface dropping during rolling increases. In addition, such selective oxidation accelerates when Al is present in the steel component, causing further danger. Therefore, the present inventors have investigated the correlation of surface defects due to the addition of P and Al, and in order to suppress the surface defects generated during hot-dip plating, it is very important to control the contents of P and Al, and to control the surface defects. It was found that Al has a functional relationship of exponential logs as in the above equation.

That is, since Al exhibits an effect of doubling grain refining effect and baking hardening property by precipitation of fine AlN in the present invention steel, it must be added more than a predetermined amount. Therefore, in the present invention, the Al content is limited to 0.15 to 0.3%. As described above, P plays a role of increasing the hardness of the hardening up to a certain amount, but excessive addition of P decreases the binding strength of the grain boundary, which is very lethal to the secondary work brittleness, and when added simultaneously with Al, the degree of embrittlement of the grain becomes very large. During cold rolling, plating defects occur after hot dip plating due to peeling of the steel sheet surface. Therefore, the P content according to the Al content should be controlled by the above formula.

Hereinafter, the manufacturing method of the present invention will be described in detail.

The steel slab that satisfies the above composition is heated at 1200 ° C. or higher and hot-rolled at a temperature range of 880 ° C. to 920 ° C. Since the austenite structure cannot be sufficiently homogenized below 1200 ° C, the austenite structure is heated to 1200 ° C or more to sufficiently homogenize. If the hot finish rolling temperature is less than 880 ℃, the material may be hardened at low hot rolling temperature. If the hot finish rolling temperature is higher than 920 ℃, the mixed structure occurs due to the abnormal reverse hot rolling, which causes defects such as orange peel after processing. easy. Therefore, hot finish rolling temperature is limited to 880 ~ 920 ℃.

After the hot rolling is wound in a temperature range of 600 ~ 650 ℃. This is to prevent the deterioration of formability due to excessive grain refinement as well as a proper grain refinement effect of 9 or more as the ASTM No. after hot rolling. When the coiling temperature exceeds 650 ℃, the grain size after annealing increases, even if the carbon and Nb content satisfies the constituent conditions presented in the present invention, sufficient grain refining effect is not obtained, and grain boundary segregation of P is increased. Secondary processing brittleness will deteriorate. When the coiling temperature is less than 600 ° C., the selective oxidation of the hot rolled pole surface layer by Al and P decreases, but the hot rolled rolling load increases. Therefore, the coiling temperature is limited to 600 ~ 650 ℃.

After hot rolling, the steel is pickled in the usual manner and cold rolled at a reduction ratio of 70 to 80%. If the reduction ratio is less than 70%, in addition to improving the aging resistance due to the grain refining effect pursued by the present invention, the effect of improving moldability, in particular, r-value cannot be obtained. In addition, when the reduction ratio is greater than 80%, the effect of grain refinement is great, but the fineness of the grain size becomes very large due to excessive rolling rate, which causes hardening of the material, and the r value gradually decreases due to excessive cold rolling rate increase. do. Therefore, the reduction ratio is limited to 70 to 80%.

Cold-rolled steel is subjected to continuous annealing or continuous melt annealing by a conventional method in the temperature range of 750 ~ 830 ℃. At this time, the temperature of the zinc plating bath (Zinc Pot) during hot dip is usually around 460 ℃, the alloying temperature at this time is managed under the conditions of 500 ~ 550 ℃. Since Nb-added steel has a higher recrystallization temperature than Ti-added steel, annealing is required at a temperature above 750 ° C. That is, when the annealing temperature is less than 750 ℃, the yield strength increases due to the presence of unrecrystallized grains, the elongation and r value deteriorates. If the annealing temperature exceeds 830 ℃ moldability is improved, but the grain size is smaller than ASTM No. 9, the grain size pursued in the present invention, Al value is 30MPa or less, the aging resistance is deteriorated.

Temper rolling is carried out at a reduction ratio of 1.2 to 1.5% using a cold rolled steel sheet manufactured by the above-described manufacturing method. The temper reduction rate of more than 1.2% is to prevent the deterioration of room temperature aging by solid carbon in the steel. However, if it is excessively increased beyond 1.5%, even though the room temperature aging resistance is improved, the temper rolling reduction rate is high, resulting in work hardening, which causes deterioration of the material. In particular, when produced by hot-dip steel sheet, the adhesion of plating is degraded by excessive temper rolling. Since the peeling of the plating layer is generated, the temper rolling rolling reduction is limited to 1.2 ~ 1.5% to solve these problems.

Hereinafter, the present invention will be described in detail through examples.

(Example)

The steel slab satisfying the composition range of the following Table 1 was heated to a temperature of 1200 ℃ or more, hot-rolled rolling in a temperature range of 880 ~ 920 ℃ and wound up to the winding temperature shown in Table 2 below. After the winding, cold rolling was performed at a reduction ratio of 70 to 80%, annealing at the annealing temperature shown in Table 2, and temper rolling was performed at a reduction ratio of 1.5%. Hot dip galvanizing was also performed. Steels 1 to 5 are invention steels satisfying the composition range of the present invention, and steels 6 to 10 are comparative steels.

Steel grade Chemical composition (% by weight) Remarks C Mn P S Sol-Al Ti Nb N Mo B One 0.0017 0.76 0.012 0.0078 0.269 0.001 0.005 0.0018 0.032 0.0005 Invention steel 2 0.0026 0.69 0.010 0.0068 0.297 0.0015 0.009 0.0022 0.049 0.0006 Invention steel 3 0.0018 0.59 0.022 0.0063 0.207 0 0.007 0.0021 0.059 0.0008 Invention steel 4 0.0021 0.98 0.042 0.0072 0.151 0.0005 0.006 0.0016 0.053 0.0009 Invention steel 5 0.0024 0.87 0.036 0.0082 0.153 0 0.006 0.0017 0.058 0.0007 Invention steel 6 0.0025 0.83 0.045 0.0076 0.052 0.001 0.01 0.0014 0.046 0.0006 Comparative steel 7 0.0012 0.75 0.039 0.0067 0.391 0.0005 0.009 0.0021 0.053 0.0009 Comparative steel 8 0.0017 0.93 0.037 0.0078 0.503 0.002 0.034 0.0018 0.034 0.0007 Comparative steel 9 0.0028 0.49 0.062 0.0069 0.411 0.0015 0.007 0.0021 0.03 0.0006 Comparative steel 10 0.0065 0.62 0.048 0.0082 0.997 0.001 0.006 0.0022 0.042 0 Comparative steel

Tensile strength, elongation, r value, hardening amount (BH), aging index (AI) and plating defects of the cold rolled steel sheets and the hot dip galvanized steel sheets prepared as described above were measured and shown in Table 2.

The test method at this time is as follows.

The r value is a measure of the change in the width direction with respect to the thickness direction, and the average r value is calculated as (r ₀ + 2r ₄₅ + r ₉₀ ) / 4, and the stiffening amount is the same in the same direction as the tensile test specimen and the test piece in the lake. After fabrication, baking was carried out at 170 ° C. for 20 minutes, and the yield strength difference before and after the measurement was measured. AI was measured in the same specimen direction and lake as the tensile specimen and measured the yield strength difference before and after 1 hour aging at 100 ° C.

Steel grade CT (℃) Annealing Temperature (℃) TS (MPa) EL (%) r value BH (MPa) AI (MPa) Plating defect Remarks One 622 803 355.8 40.3 2.08 55.5 24.8 ⊙ Invention steel 2 618 812 357.3 40.5 2.11 52.8 22.6 ⊙ Invention steel 3 624 784 361.4 41.2 2.23 47.6 18.9 ⊙ Invention steel 4 634 792 357.9 40.0 2.02 53.0 25.1 ⊙ Invention steel 5 656 818 367.8 40.2 2.04 51.5 24.7 ⊙ Invention steel 6 615 811 401.6 37.2 1.74 42.0 18.7 ⊙ Comparative steel 7 623 810 368.9 39.8 1.96 0.0 0.0 ⊙ Comparative steel 8 631 805 391.4 39.5 1.92 0.0 0.0 ⊙ Comparative steel 9 622 812 349.3 40.2 2.01 47.0 21.9 × Comparative steel 10 617 805 353.8 37.4 1.72 75.1 48.0 ⊙ Comparative steel Plating defects: ⊙ (within 10 defects per km), △ (within 10-100 defects per km), × (with more than 100 defects per km)

As shown in Table 2, the inventive steels 1 to 5, which strictly control the amounts of C, P, Ti, Nb, Sol-Al, Mo, and the like, have a bake hardening amount (BH) of 30 MPa or more and an aging index ( AI) value satisfies 30 MPa or less and has a high tensile strength of 340 MPa grade.

Comparative steel 6 added 0.052% of the content of Sol-Al lower than that proposed in the present invention, so that even if the winding and annealing temperature proposed in the present invention were maintained, the elongation was 37.2% and the r value of 1.74 was 40. Elongation of% or more and r value of 2.0 or more are not satisfied.

Comparative steel 7 had a very low C content of 0.0012% and a high Sol-Al content. Therefore, the carbon content was so low that BH properties could not be expected, and the elongation and r value were lowered.

Comparative steel 8 has a very high content of Sol-Al (0.503%), the elongation and r value is out of the range suggested by the present invention, the content of Nb is added very high (0.034%) so that Nb is combined with C in the steel, The BH value was not obtained because it did not exist at all.

In the case of Comparative Steel 9, the other components satisfy the conditions of the present invention, but the P content was added as high as 0.062%. Since P and Sol-Al are added at the same time, P ≦ −0.06 * ln (Al) -0.0018 / Al-0.055 is not satisfied. Therefore, the surface oxide increased from the hot rolling step due to the excessive addition of P, and accordingly, surface defects such as linear defects occurred more than 100 per km when the hot-dip material was manufactured.

In comparison, the C content was higher as 0.0065% of the C content exceeding the range suggested by the present invention, and the BH property, as well as the AI value of 30 MPa or more, resulted in deterioration of aging resistance at room temperature. In addition, Sol-Al was very high at 0.997%, and the elongation and r value did not satisfy the criteria suggested by the present invention.

1 shows an electron scanning microscope of fine defects of linear defects.

Figure 2 shows the results of the analysis of the fine oxide and EDS formed on the grain boundary surface of the metal surface at high temperature winding of 750 ℃.

Figure 3 shows the mechanical properties according to the Al content.

Figure 4 shows the phase change according to the Al content.

Claims (12)

By weight%, C: 0.0016 ~ 0.0030%, Si: 0.02% or less, Mn: 0.2 ~ 1.2%, P: 0.01 ~ 0.05%, S: 0.01% or less, Soluble Al: 0.15 ~ 0.3%, N: 0.0025 % Or less, Nb: 0.003-0.011%, Mo: 0.01-0.1% and B: 0.0005-0.0015%, the remainder is composed of Fe and unavoidable impurities, and the content of P and Sol-Al is P≤-0.06 * High strength hardened hardened cold rolled steel sheet, characterized by satisfying ln (Al) -0.0018 / Al-0.055. According to claim 1, wherein the steel sheet is a high-strength hardened cold-rolled steel sheet, characterized in that it further comprises Ti: 0.003% or less. The high-strength sintered steel sheet according to claim 1 or 2, wherein the cold-rolled steel sheet has a bake hardening (BH) value of 30 MPa or more, an aging index (AI) of 30 MPa or less, and a grain size of ASTM No. 9 or more. Hardened Cold Rolled Steel Sheet By weight%, C: 0.0016 ~ 0.0030%, Si: 0.02% or less, Mn: 0.2 ~ 1.2%, P: 0.01 ~ 0.05%, S: 0.01% or less, Soluble Al: 0.15 ~ 0.3%, N: 0.0025 % Or less, Nb: 0.003-0.011%, Mo: 0.01-0.1% and B: 0.0005-0.0015%, the remainder is composed of Fe and unavoidable impurities, and the content of P and Sol-Al is P≤-0.06 * A high-strength hardening type hot-dip galvanized steel sheet which satisfies ln (Al) -0.0018 / Al-0.055 and comprises a hot-dip galvanized layer. The high-strength hardening type hot dip galvanized steel sheet according to claim 4, wherein the steel sheet further comprises Ti: 0.003% or less. The hot-dip galvanized steel sheet has a bake hardening (BH) value of 30 MPa or more, an aging index (AI) of 30 MPa or less, and a grain size of ASTM No. 9 or more. High strength bake hardened hot dip galvanized steel sheet. By weight%, C: 0.0016 ~ 0.0030%, Si: 0.02% or less, Mn: 0.2 ~ 1.2%, P: 0.01 ~ 0.05%, S: 0.01% or less, Soluble Al: 0.15 ~ 0.3%, N: 0.0025 % Or less, Nb: 0.003-0.011%, Mo: 0.01-0.1% and B: 0.0005-0.0015%, the remainder is composed of Fe and unavoidable impurities, and the content of P and Sol-Al is P≤-0.06 * heating the steel slab satisfying ln (Al) -0.0018 / Al-0.055 at 1200 ° C. or higher and then hot finishing rolling in a temperature range of 880 ° C. to 920 ° C .; Air cooling after winding in a temperature range of 600 to 650 ° C .; Cold rolling at a reduction ratio of 70-80%; Continuous annealing at a temperature range of 750 ~ 830 ℃; And Temper rolling at 1.2 ~ 1.5% reduction rate Method for producing a high-strength hardened hardened cold rolled steel sheet comprising a. 8. The method of claim 7, wherein the steel slab further comprises Ti: 0.003% or less. The method for producing a high strength hardened hardened cold rolled steel sheet according to claim 7 or 8, wherein the continuous annealing is performed so that the size of the grain after annealing is equal to or higher than ASTM No. 9. By weight%, C: 0.0016 ~ 0.0030%, Si: 0.02% or less, Mn: 0.2 ~ 1.2%, P: 0.01 ~ 0.05%, S: 0.01% or less, Soluble Al: 0.15 ~ 0.3%, N: 0.0025 % Or less, Nb: 0.003-0.011%, Mo: 0.01-0.1% and B: 0.0005-0.0015%, the remainder is composed of Fe and unavoidable impurities, and the content of P and Sol-Al is P≤-0.06 * heating the steel slab satisfying ln (Al) -0.0018 / Al-0.055 at 1200 ° C. or higher and then hot finishing rolling in a temperature range of 880 ° C. to 920 ° C .; Air cooling after winding in a temperature range of 600 to 650 ° C .; Cold rolling at a reduction ratio of 70-80%; Continuous annealing at a temperature range of 750 ~ 830 ℃; Temper rolling at a reduction ratio of 1.2 to 1.5%; And Hot dip galvanizing step Method for producing a high strength bake hardened hot-dip galvanized steel sheet comprising a. 12. The method of claim 10, wherein the steel slab further comprises Ti: 0.003% or less. The method for producing a high strength hardened hardened zinc plated steel sheet according to claim 10 or 11, wherein the continuous annealing is performed such that the size of the crystal grains after annealing is equal to or higher than ASTM No. 9.

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